Tim Cahill waged a farcical campaign for governor in 2010, but that barely accounts for the tragedy that may be unfolding now in Suffolk Superior Court.

The former state treasurer landed at the defendant’s table for allegedly using public money to promote the lottery while he was running as a third-party candidate seeking to topple Governor Deval Patrick. He is now about halfway through a trial expected to last six weeks.

If the state is to be believed, the ad campaign was a back-door way of connecting Cahill with the popular lottery and amounted to using public money to promote his candidacy.

I’ve been puzzled by the prosecution’s argument from the day it was announced. Politicians routinely use their accomplishments in office to promote their candidacy. Any voter who has ever seen a campaigning politician brag about, say, their latest public works project is understandably at a loss to grasp what, exactly, Cahill did wrong.

The trial concludes a saga that was bizarre from the start. From the beginning, the Cahill campaign was plagued by a question no campaign should have trouble answering: Why is he running?

Cahill was a popular enough state treasurer, and when he decided to run Patrick was not an especially popular governor. Still, Cahill’s bid never seemed destined to rise above “spoiler” status; he never had any chance of beating Patrick or GOP nominee Charlie Baker. The most popular explanation for his third-party run was that he was feuding with Patrick — or perhaps with Patrick’s
advisers, who had previously advised him. The problem with that theory was that Patrick was the candidate who seemed to benefit from having Cahill in the race, with Baker and Cahill splitting the anti-Patrick vote.

Truly, the whole thing was a head-scratcher.

Cahill’s career seemed to have reached its nadir on the day that his running mate, Paul Loscocco, decided to bolt the ticket rather than continue his run for lieutenant governor. In fairness, it did prompt the most memorable line of Cahill’s career: “I’m not planning to die, so we can just abolish that useless office.”

When it comes to public corruption we live in uncertain times. Some cases, like the small-time thefts of Dianne Wilkerson and Chuck Turner, are obvious. The long-running investigation of the Probation Department by the US Attorney’s Office prompts a more ambivalent reaction.

Then, there is Cahill. He ran ads he doesn’t even appear in. Granted, they promoted a popular agency that he oversaw, but promoting the lottery isn’t a crime. How many Powerball ads ran this weekend? Did you even think about Steve Grossman, the current treasurer, as you watched them?

Just what is the crime here?

Cahill’s campaign left him with few friends in either party. Even without a criminal investigation hanging over his head he wasn’t equipped to move into a career in high finance; everyone knew that other people in his office handled the sophisticated financial decisions. Since being indicted his life has revolved around simply trying to stay out of prison.

After Cahill was indicted, I asked a veteran prosecutor what he thought of the case. Granted anonymity to speak his mind he said, “I think it’s complete nonsense. A huge part of being a prosecutor is judgment. You’re supposed to use your power judiciously; you don’t charge people just because you can. I think the judgment on this call was terrible.”

Like many people, I’ve never had strong feeling about Tim Cahill one way or the other. Basically, I think of him as a Quincy city councilor who got lucky and landed in a higher office than his skills predicted.

But he certainly can’t be feeling lucky now. For routine ads in a race in which he was clobbered, he faces the very real prospect of prison. His true error in judgment wasn’t running ads for himself, it was running for governor.